Primitive Archer
Main Discussion Area => Bows => Topic started by: Susquehannock on May 31, 2008, 07:53:27 pm
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Here is my first attempt at a BBO. This bow is currently pulling low 50#s @ 19". It is 59" ntn and about 1-1/4" wide. I am hoping to hit around 55# @ my 26" draw. Let me know what you think about the tiller so far. I have included one of those circular guides as someone else uses. I have been tillering mainly using my digital camera to see where I am. I scrape a little, take a pic, run to the computer, and analyze. I think I have been looking at it too long, so some objective feedback will be helpful.
Thanks, Jason
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hey
looks like the left side has more curve to it, but that the right side dives out of the fades more abruptly.
Right side: leave alone at the fades, gradually scrape out the outer 2/3 of the limb.
Left side: evenly remove a thin layer from the fades out to about 2/3...then remove wood a little more aggressively, to get some bend happening in that flat spot.
BBO's are cool...i've only built 2 of them, but I found they were stiffer under the nodes...You can get a lot of weight from this combo, so don't be surprised if your osage winds up quite thin.
Jim Hamm said to get the tiller even and THEN go for weight. So you might want to refrain from drawing any further than 19" until the arcs are smooth and even. The weight will drop, maybe as much as 10 #...but you will have even tiller and as you begin to draw it further, it should be quite easy to reach your desired draw weight or even a little higher.
radius
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Your starting to hinge on the left limb about 8 inches off the fade. You need to scrape on either side of the hinge to correct it..dont pull the bow any farther until you have it working more evenly or its going to take undue set on that limb. I like the tiller on the right limb just scrape it evenly to keep it in time with the other side. Good luck!
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Thanks for the feedback guys. It's helpful to get another point of view. I see hinges on the left about 8" off fade and on the right about 10" off fade that I didn't see before I asked. Sometimes it pays to put the bow up for the night and get some advice before plowing ahead. I really like tillering with the digital camera. It lets me take my time and really study the bend.
Thanks, Jason
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I think I have worked out the hinges beyond the fades.
Question for you bamboo people: At what stage do you scrape the rind off your boo, and will this affect draw weight by any substantial measurement?
Thanks, Jason
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You can scrape off the rind at any time. Doing so will not affect the draw weight.
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great advice,,, if done right will make a nice bow,,,, go slow,,,, dont overdraw earley,,, nice job....snake
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dumb question:
How do you do the circular guide?
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I'd stay away from the fade on both limbs. It doesn't look like you have much meat left on either side. I'd forget the red lines too. It doesn't match the tiller you are looking at and if you try to you won't have the weight you want.
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Mullet,
I have continued scraping the middle and outer limbs and haven't touched the fades. You are right, the osage is really thin (rookie mistake in that the boo was a bit too thick to begin with). The right limb looks like all boo, but in fact I have a small amount of osage sapwood in the belly of this bow.
Loco, I did the circular guide with photoshop. I saw someone else use this to help them on this site, but honestly, I think using the digital camera and analyzing after each wood removal session has helped me the most building this bow.
Thanks for the feedback everyone.
Jason
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Here is the same bow drawn 2 more inches to about 21". I think the limbs are flipped in this picture from the last pics I posted, and I have added some layers of wood to the handle to give it some visual appeal.
Jason
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I would still work the outer limbs,starting about 4" in from the knocking point. And then work your way towards the mid section ,SLOWLY. Scrape a little and then check it.If your limbs are wide enougth you can scrape the sides and trap the boo. That way you can keep from scraping all the Osage away.
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Mullet, when you say "trap" the boo, do you mean bevel/round the corners of the boo? Right now the limbs are around 1-1/4" wide, so I think I have plenty of width to tiller off the sides and I was already thinking that's what I should do since the osage is getting thin.
Jason
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Yea thats what I mean. Angle in on the sides and when you are finished,round the edges off a little.
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The left limb in that picture looks hingey right before the tip I would stay away from that area.
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Well, Ryan was right. I started to tiller some more and noticed that both tips are a little hingy about 4-5" out from the knocks. I could kick myself for not seeing it, but I guess I was trying to get more bend out of a shorter bow.
What are my options to fix the tips?
1) cut the tips down a little--Right now I'm at 57-1/2" knock to knock, so will a shorter bow be able to handle any reduction in length given my 55# @ 26" draw goal? I know bbo is a strong combination, but this is the shortest bow I have built so I'd like to hear what others think.
2) glue a thin hardwood overlay to reinforce and stiffen the last 4-5"? If so, should this be glued to the back or the belly?
Thanks for the feedback.
Jason
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As an aside Jason, I posted a method I use to visualize exactly where your limbs bend here:
http://www.primitivearcher.com/smf/index.php/topic,4820.0.html
Since you like digicams I thought you might be interested.
Dave
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Thanks David,
Well, when it rains, it pours. I think this bow has definitely been a learning experience thus far. After I noticed the hinges on the tips, I gently took it out in the garage and floor tiller flexed the tip. CRACK! The osage started to crush/break right where the hinge was. The bamboo is still in perfect condition. (see pics below). The osage separated at the glue line the remainder of the length of the tip. I have debated wether to cut it down and make it a kids bow, or try to fix. I think I will see if I can fix it and worse case scenario cut it down for a bow for my son.
I have superglued/wood glued and clamped the separated part and where the osage started to crack. After the glue dries, I plan to taper the belly flat the last 6" on both tips and glue on a thin hardwood strip on both ends, then sand it smooth. I will probably wrap those spots with sinew or thread for insurance. What does everybody think?
Jason
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